Extensive research has shown that premature infants suffer impaired physical, social and cognitive development. The major focus of the proposed project is to facilitate their development through an intervention program of early sensory stimulation. Such stimulation is now recognized as critical to normal development. To offset the relative "sensory deprivation" typically suffered in the isolette, intervention will begin shortly after birth and extend throughout the premature's hospitalization (approximately 2 months). The intervention program will consist of daily periods of stimulation in the visual, auditory, tactual, and vestibular modalities. Its effectiveness will be assessed throughout the first half-year of life by comparison with control groups on a variety of tasks. These assessments will focus on tasks which measure arousal level, visual attentiveness, social responsivity, and rate of mental development because there is evidence to suggest that these tasks are highly interrelated and sensitive to early experiences. Ages for testing have been worked out so as to allow comparisons between premature and full-term infants matched for both chronological and gestational age. The analyses will focus on (1) assessing the impact of sensory enrichment on development (2) determining whether any of the early behaviors predict later functioning and (3) answering questions having to do with the stability and interrelationship of performance on the various measures.